where \(\sigma _{\rm con}=C/s^{\lambda }\)  represents the continuum amplitude with the
unknown exponent \(\lambda \)  and a constant \(C\) ;
the resonance \(\psi \)  has a fixed mass \(M\)  and total width \(\Gamma \)  [1]};
the factor \(f_{\sigma _{\psi }}=\sigma (e^+e^-\rightarrow \psi \rightarrow p\bar{p}\pi ^0)\)  is the peak cross section of the resonance \(\psi \) ;
the parameter \(\phi \)  describes the relative phase between the continuum
and resonance amplitudes.
